CN114464887B - Secondary battery - Google Patents

Secondary battery Download PDF

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CN114464887B
CN114464887B CN202111647802.8A CN202111647802A CN114464887B CN 114464887 B CN114464887 B CN 114464887B CN 202111647802 A CN202111647802 A CN 202111647802A CN 114464887 B CN114464887 B CN 114464887B
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positive electrode
compound
equal
less
secondary battery
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CN114464887A (en
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邓永红
钱韫娴
胡时光
林雄贵
李红梅
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Shenzhen Capchem Technology Co Ltd
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Shenzhen Capchem Technology Co Ltd
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Priority to EP22821833.5A priority patent/EP4231406A1/en
Priority to PCT/CN2022/132197 priority patent/WO2023124604A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/502—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

In order to overcome the problems of insufficient high temperature cycle and high temperature storage performance of the battery caused by manganese ion dissolution of the existing manganese-based positive electrode material battery, the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the positive electrode active material comprises a manganese-based material, the nonaqueous electrolyte comprises a solvent, electrolyte salt and an additive, and the additive comprises a compound shown in a structural formula 1:the secondary battery satisfies the following conditions: 0.05-100 XWXu/(qXs) 5, 2.0-4.5 g/Ah, 0.05-3.5% u, 5-65% q, 10mg/cm 2 ≤s≤30mg/cm 2 . The secondary battery provided by the invention has higher capacity retention rate in the circulating and high-temperature storage processes, and has better circulating performance and storage performance.

Description

Secondary battery
Technical Field
The invention belongs to the technical field of energy storage battery devices, and particularly relates to a secondary battery.
Background
Since the commercialized application of the lithium ion battery in the 90 th century of 20 th year, the lithium ion battery has the advantages of high voltage platform, high energy density, wider temperature application range, low self-discharge, no memory effect, environmental friendliness and the like, is widely applied to the fields of 3C digital products such as mobile phones, notebook computers and the like, and is rapidly permeated and developed in the fields of new energy automobiles and large energy storage in recent years.
With the continuous maturity of lithium ion battery technology, end users put higher demands on the safety performance of lithium ion batteries. The element composition of the positive electrode active material in the lithium ion battery has an important influence on the safety performance of the battery, and the safety performance of the lithium ion battery can be improved by adopting the positive electrode active material with higher manganese element content; meanwhile, the price of manganese is low, the proportion of noble metals in the material can be reduced, and the market application of the lithium ion battery is promoted. However, as the trivalent manganese element in the positive electrode is easy to perform disproportionation reaction to generate divalent manganese ions which are soluble in electrolyte, so that the divalent manganese ions catalyze the oxidative decomposition of the electrolyte, and in addition, the manganese ions which migrate to the surface of the negative electrode are reduced, the structure of the negative electrode SEI film can be destroyed, the electrolyte is catalyzed to be continuously decomposed on the surface of the negative electrode, so that active lithium is lost, the capacity attenuation is accelerated, the cycle performance and the storage performance of the lithium ion battery are deteriorated, and the influence of the lithium ion battery under the high-temperature condition is more serious.
Disclosure of Invention
Aiming at the problems of insufficient high-temperature circulation and high-temperature storage performance of the battery caused by dissolution of manganese ions in the conventional manganese-based positive electrode material battery, the invention provides a secondary battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the positive electrode active material comprises a manganese-based material, the nonaqueous electrolyte comprises a solvent, electrolyte salt and an additive, and the additive comprises a compound shown in a structural formula 1:
wherein n is 0 or 1, A is selected from C or O, and X is selected fromR 1 、R 2 Each independently selected from H, & gt> R 1 And R is 2 Not simultaneously selected from H, and X, R 1 And R is 2 Contains at least one sulfur atomA seed;
the secondary battery satisfies the following conditions:
0.05≤100×W×u/(q×s)≤5
w is more than or equal to 2.0g/Ah and less than or equal to 4.5g/Ah, u is more than or equal to 0.05% and less than or equal to 3.5%, q is more than or equal to 5% and less than or equal to 65%, and 10mg/cm 2 ≤s≤30mg/cm 2 ；
Wherein W is the ratio of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery, and the unit is g/Ah;
u is the mass percentage content of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is;
q is the mass percentage content of manganese element in the positive electrode material layer, and the unit is;
s is the single-sided area density of the positive electrode material layer, and the unit is mg/cm 2 。
Alternatively, the secondary battery satisfies the following condition:
0.1≤100×W×u/(q×s)≤4。
optionally, the ratio W of the mass of the non-aqueous electrolyte to the rated capacity of the secondary battery is 2.0-4.0 g/Ah.
Optionally, the mass percentage content u of the compound shown in the structural formula 1 in the nonaqueous electrolyte is 0.05% -3.0%.
Optionally, the mass percentage q of the manganese element in the positive electrode material layer is 5% -50%.
Optionally, the single-sided surface density s of the positive electrode material layer is 15-25 mg/cm 2 。
Optionally, the compound represented by the structural formula 1 is selected from one or more of the following compounds 1 to 22:
optionally, the positive electrode active material is selected from one or more of compounds represented by formula (a) and formula (B):
Li 1+x Ni a Co b M’ 1-a-b O 2-y A y (A)
Li 1+z Mn c L 2-c O 4-d K d (B)
In the formula (A), x is more than or equal to 0.1 and less than or equal to 0.2,0 is less than or equal to a <1,0 is less than or equal to b is less than or equal to 1,0 is less than or equal to a+b is less than 1,0 is less than or equal to y is less than or equal to 0.2, M' comprises Mn, and comprises Al, sr, mg, ti, ca, zr, zn, si, fe, zero species, one or more species of Ce, A comprises S, N, F, B, cl, br and one or more species of I;
in the formula (B), z is more than or equal to-0.1 and less than or equal to 0.2, c is more than or equal to 0 and less than or equal to 2, d is more than or equal to 0 and less than or equal to 1, L comprises one or more of Ni, fe, cr, ti, zn, V, al, mg, zr and Ce, and K comprises one or more of S, N, F, B, cl, br and I.
Optionally, the nonaqueous electrolyte further comprises an auxiliary additive, wherein the auxiliary additive comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound;
Preferably, the additive amount of the auxiliary additive is 0.01 to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
Optionally, the cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate;
the sultone compound is at least one selected from methyl disulfonic acid methylene ester, 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;
the cyclic carbonate compound is at least one selected from ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,
in the structural formula 2, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group;
the phosphate compound is at least one selected from tri (trimethylsilane) phosphate and a compound shown in a structural formula 3:
in the structural formula 3, R 31 、R 32 、R 32 Each independently selected from the group consisting of C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
the borate compound is selected from tris (trimethylsilane) borate;
the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanedinitrile, adiponitrile, pimelic dinitrile, suberonitrile, nonyldinitrile and decyldinitrile.
According to the secondary battery provided by the invention, the manganese-based material is adopted as the main component of the positive electrode active material, so that the structural stability of the material is better, the material can endure more severe structural damage, the thermal runaway effect caused by the structural damage of the material at high temperature is reduced, the side reaction of electrolyte on a solid-liquid interface inside the battery is reduced, and the gas production and heat production inside the battery are reduced, thereby effectively improving the safety performance of the secondary battery; meanwhile, a compound shown in a structural formula 1 is added into the nonaqueous electrolyte, and the ratio of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery and the parameter range of the single-sided surface density of the positive electrode material layer are controlled to enable the ratio to meet the relation of 0.05-100 XW-U/(q-s) to be less than or equal to 5, so that a compact passivation film can be formed at a positive electrode interface, a positive electrode structure is stabilized, the dissolution of manganese ions is reduced, and the oxidative decomposition of the electrolyte on the positive electrode interface is reduced; meanwhile, the compound shown in the structural formula 1 can also form a protective film on the anode, so that the damage of dissolved manganese ions to the anode SEI film structure is obviously reduced, the continuous decomposition of electrolyte at the anode interface is effectively inhibited, the loss of active lithium is reduced, the stability of the anode interface is improved, and the lower interface impedance and the proper viscosity of the electrolyte are ensured, so that the capacity retention rate of the secondary battery in the circulating and high-temperature storage processes is improved while the higher capacity exertion and the multiplying power charge-discharge performance of the secondary battery are ensured, and the better high-temperature circulating performance and storage performance are obtained.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the positive electrode active material comprises a manganese-based material, the nonaqueous electrolyte comprises a solvent, electrolyte salt and an additive, and the additive comprises a compound shown in a structural formula 1:
wherein n is 0 or 1, A is selected from C or O, and X is selected fromR 1 、R 2 Each independently selected from H, & gt> R 1 And R is 2 Not simultaneously selected from H, and X, R 1 And R is 2 Contains at least one sulfur atom;
the secondary battery satisfies the following conditions:
0.05≤100×W×u/(q×s)≤5
w is more than or equal to 2.0g/Ah and less than or equal to 4.5g/Ah, u is more than or equal to 0.05% and less than or equal to 3.5%, q is more than or equal to 5% and less than or equal to 65%, and 10mg/cm 2 ≤s≤30mg/cm 2 ；
Wherein W is the ratio of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery, and the unit is g/Ah;
u is the mass percentage content of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is;
q is the mass percentage content of manganese element in the positive electrode material layer, and the unit is;
s is the single-sided area density of the positive electrode material layer, and the unit is mg/cm 2 。
The manganese-based material is adopted as the main component of the positive electrode active material, so that the material has better structural stability, can endure more severe structural damage, reduces the thermal runaway effect caused by the structural damage of the material at high temperature, reduces the side reaction of electrolyte on the solid-liquid interface inside the battery, and reduces the gas production and heat production inside the battery, thereby effectively improving the safety performance of the secondary battery; meanwhile, a compound shown in a structural formula 1 is added into the nonaqueous electrolyte, and the ratio of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery and the parameter range of the single-sided surface density of the positive electrode material layer are controlled to enable the ratio to meet the relation of 0.05-100 XW-U/(q-s) to be less than or equal to 5, so that a compact passivation film can be formed at a positive electrode interface, a positive electrode structure is stabilized, the dissolution of manganese ions is reduced, and the oxidative decomposition of the electrolyte on the positive electrode interface is reduced; meanwhile, the compound shown in the structural formula 1 can also form a protective film on the anode, so that the damage of dissolved manganese ions to the anode SEI film structure is obviously reduced, the continuous decomposition of electrolyte at the anode interface is effectively inhibited, the loss of active lithium is reduced, the stability of the anode interface is improved, and the lower interface impedance and the proper viscosity of the electrolyte are ensured, so that the capacity retention rate of the secondary battery in the circulating and high-temperature storage process is improved while the higher capacity exertion and the multiplying power charge-discharge performance of the secondary battery are ensured, and the better circulating performance and storage performance are obtained.
In some embodiments, when n is 0, the compound of formula 1 is:
wherein A is selected from C or O and X is selected fromR 1 、R 2 Each independently selected from H,R 1 And R is 2 Not simultaneously selected from H, and X, R 1 And R is 2 Contains at least one sulfur atom.
In some embodiments, when n is 1, the compound of formula 1 is:
wherein A is selected from C or O and X is selected fromR 1 、R 2 Each independently selected from H,R 1 And R is 2 Not simultaneously selected from H, and X, R 1 And R is 2 Contains at least one sulfur atom.
In a preferred embodiment, the secondary battery satisfies the following conditions:
0.1≤100×W×u/(q×s)≤4。
the ratio W of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery, the mass percentage u of the compound shown in the structural formula 1 in the nonaqueous electrolyte, the mass percentage q of the manganese element in the positive electrode material layer and the single-sided surface density s of the positive electrode material layer are related, so that the influences of the additive and the positive electrode active material selection in the nonaqueous electrolyte on the high-temperature cycle and the high-temperature storage performance of the battery can be comprehensively combined, and the secondary battery with excellent high-temperature cycle and high-temperature storage performance can be obtained.
Specifically, the ratio W of the mass of the nonaqueous electrolytic solution to the rated capacity of the secondary battery was 2.0g/Ah, 2.1g/Ah, 2.3g/Ah, 2.5g/Ah, 2.7g/Ah, 2.9g/Ah, 3.0g/Ah, 3.2g/Ah, 3.4g/Ah, 3.6g/Ah, 3.8g/Ah, 4.0g/Ah, 4.1g/Ah, 4.3g/Ah and 4.5g/Ah.
In a preferred embodiment, the ratio W of the mass of the nonaqueous electrolytic solution to the rated capacity of the secondary battery is 2.0 to 4.0g/Ah.
The ratio W of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery determines the relative mass of the anode and cathode materials in the battery and the nonaqueous electrolyte, while the mass percentage u of the mass of the nonaqueous electrolyte and the mass percentage u of the compound shown in the structural formula 1 in the nonaqueous electrolyte determines the total addition amount of the compound shown in the structural formula 1 in the secondary battery.
Specifically, the mass percentage u of the compound represented by structural formula 1 in the nonaqueous electrolytic solution is 0.05%, 0.1%, 0.12%, 0.15%, 0.3%, 0.5%, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.7%, 1.9%, 2.1%, 2.2%, 2.4%, 2.7%, 2.9%, 3.1%, 3.3% or 3.5%.
In a preferred embodiment, the mass percentage content u of the compound shown in the structural formula 1 in the nonaqueous electrolyte is 0.05% -3.0%.
If the content of the compound shown in the structural formula 1 in the nonaqueous electrolyte is too low, the dissolution of manganese ions cannot be effectively inhibited, the stability of the positive and negative electrode interfaces is reduced, and if the content of the compound shown in the structural formula 1 in the nonaqueous electrolyte is too high, the interface impedance is too high, so that the performance of battery capacity and multiplying power charge and discharge performance is not facilitated.
Specifically, the mass percentage q of the manganese element in the positive electrode material layer is 5%, 8%, 10%, 12%, 15%, 19%, 22%, 25%, 29%, 31%, 35%, 37%, 39%, 40%, 43%, 46%, 48%, 50%, 51%, 54%, 57%, 58%, 62%, 64% or 65%.
In a preferred embodiment, the mass percentage q of the manganese element in the positive electrode material layer is 5% -50%.
If the q value of the mass percent of the manganese element in the positive electrode material layer is too low, the safety performance of the secondary battery is reduced; if the mass percentage q value of the manganese element in the positive electrode material layer is too high, the capacity exertion and the high-temperature storage performance of the secondary battery are affected.
Specifically, the single-sided surface density s of the positive electrode material layer was 10mg/cm 2 、12mg/cm 2 、15mg/cm 2 、19mg/cm 2 、21mg/cm 2 、22mg/cm 2 、24mg/cm 2 、26mg/cm 2 、29mg/cm 2 Or 30mg/cm 2 。
In a preferred embodiment, the single-sided surface density s of the positive electrode material layer is 15 to 25mg/cm 2 。
When the single-sided area density s of the positive electrode material layer is in the above range, effective exertion of the positive electrode active material capacity can be ensured. The single-sided surface density s of the positive electrode material layer is too low, so that available lithium ions are less, the battery capacity is low, and the energy density of the battery is not improved; the single-sided surface density s of the positive electrode material layer is too high, which indicates that the slurry coated on the positive electrode is too much, which is not beneficial to the full infiltration of the nonaqueous electrolyte, prolongs the migration path of lithium ions and electrons, influences the capacity and multiplying power performance of the battery, and especially when the battery reaches the end of circulation, the phenomenon that the retention rate of the circulation capacity of the battery suddenly decays rapidly easily occurs, even the battery generates gas, which is not beneficial to the circulation life of the battery, and also brings safety risks.
In the description of the present invention, the term "single-sided areal density of a positive electrode material layer" refers to the coating quality of the positive electrode material layer on a single side of a positive electrode sheet per unit area, and the coating quality test method may employ the following means: taking 30 pieces of current collector foil, wherein the area of each piece is A1, respectively weighing the mass of each piece, taking the average value of the mass, and recording the average value as s1; coating the same-quality slurry on one side of each current collector foil, uniformly coating, drying at 120 ℃ for 1 hour, detecting to basically not contain solvent, respectively weighing the mass of the current collector foil coated with the slurry on one side after drying, taking the average value of the mass, and recording as s2; the areal density s= (s 2-s 1)/A1 of the positive electrode material layer located on one side of the current collector can be obtained.
The analysis is based on the influence of each parameter or a plurality of parameters on the battery only when the parameters exist alone, but in the practical battery application process, the ratio W of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery, the mass percentage u of the compound shown in the structural formula 1 in the nonaqueous electrolyte, the mass percentage q of the manganese element in the positive electrode material layer, the single-sided surface density s of the positive electrode material layer and other parameters have certain internal relations, and the inventor can summarize that the relation is 0.05-100 XW/(q-s) 5, and can be effectively used as the basis for screening the secondary battery with excellent cycle performance and storage performance at high temperature through a large number of experiments.
In some embodiments, the compound of formula 1 is selected from one or more of the following compounds 1-18:
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the above is only a preferred compound of the present invention, and does not represent a limitation of the present invention.
The preparation method of the above-mentioned compound can be known to those skilled in the art based on common general knowledge in the field of chemical synthesis, knowing the structural formula of the compound represented by structural formula 1. For example: compound 7 can be made by the following method:
placing sorbitol, dimethyl carbonate, a methanol alkaline substance catalyst potassium hydroxide, DMF and other organic solvents in a reaction vessel, reacting for a plurality of hours under the heating condition, adding a certain amount of oxalic acid to adjust the pH to be neutral, filtering, recrystallizing to obtain an intermediate product 1, esterifying the intermediate product 1, the carbonate, thionyl chloride and the like under the high temperature condition to obtain an intermediate product 2, and oxidizing the intermediate product 2 by using an oxidant such as sodium periodate and the like to obtain the compound 7.
In some embodiments, the positive electrode active material is selected from one or more of compounds represented by formula (a) and formula (B):
Li 1+x Ni a Co b M’ 1-a-b O 2-y A y (A)
Li 1+z Mn c L 2-c O 4-d K d (B)
In the formula (A), x is more than or equal to 0.1 and less than or equal to 0.2,0 is less than or equal to a <1,0 is less than or equal to b is less than or equal to 1,0 is less than or equal to a+b is less than 1,0 is less than or equal to y is less than or equal to 0.2, M' comprises Mn, and comprises Al, sr, mg, ti, ca, zr, zn, si, fe, zero species, one or more species of Ce, A comprises S, N, F, B, cl, br and one or more species of I;
in the formula (B), z is more than or equal to-0.1 and less than or equal to 0.2, c is more than or equal to 0 and less than or equal to 2, d is more than or equal to 0 and less than or equal to 1, L comprises one or more of Ni, fe, cr, ti, zn, V, al, mg, zr and Ce, and K comprises one or more of S, N, F, B, cl, br and I.
In some embodiments, the positive electrode further comprises a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector. The portions of the positive electrode other than the positive electrode current collector are referred to as positive electrode material layers in this application.
The positive current collector is selected from a metal material that can conduct electrons, preferably, the positive current collector includes one or more of Al, ni, tin, copper, stainless steel, and in a more preferred embodiment, the positive current collector is selected from aluminum foil.
In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent.
In some embodiments, the positive electrode binder includes a thermoplastic resin such as polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; an acrylic resin; and one or more of styrene butadiene rubber.
In some embodiments, the positive electrode conductive agent includes one or more of a metal conductive agent, a carbon-based material, a metal oxide-based conductive agent, and a composite conductive agent. Specifically, the metal conductive agent can be copper powder, nickel powder, silver powder and other metals; the carbon-based material may be a carbon-based material such as conductive graphite, conductive carbon black, conductive carbon fiber, or graphene; the metal oxide conductive agent may be tin oxide, iron oxide, zinc oxide, etc.; the composite conductive agent can be composite powder, composite fiber and the like. More specifically, the conductive carbon black may be one or more of acetylene black, 350G, ketjen black, carbon fiber (VGCF), and Carbon Nanotubes (CNTs).
In some embodiments, the electrolyte salt comprises one or more of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt. In a preferred embodiment, the electrolyte salt is selected from lithium salts or sodium salts.
In a preferred embodiment, the electrolyte salt is selected from LiPF 6 、LiPO 2 F 2 、LiBF 4 、LiBOB、LiSbF 6 、LiAsF 6 、LiCF 3 SO 3 、LiDFOB、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiN(SO 2 C 2 F 5 ) 2 、LiN(SO 2 F) 2 、LiCl、LiBr、LiI、LiClO 4 、LiBF 4 、LiB 10 Cl 10 、LiAlCl 4 At least one of lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenyl borate, and lithium iminoborate. Specifically, the electrolyte salt may be LiBF 4 、LiClO 4 、LiAlF 4 、LiSbF 6 、LiTaF 6 、LiWF 7 An inorganic electrolyte salt; liPF (LiPF) 6 An isophosphoric acid electrolyte salt; liWOF 5 Isopolytics electrolyte salts; HCO (hydrogen chloride) 2 Li、CH 3 CO 2 Li、CH 2 FCO 2 Li、CHF 2 CO 2 Li、CF 3 CO 2 Li、CF 3 CH 2 CO 2 Li、CF 3 CF 2 CO 2 Li、CF 3 CF 2 CF 2 CO 2 Li、CF 3 CF 2 CF 2 CF 2 CO 2 Carboxylic acid electrolyte salts such as Li; CH (CH) 3 SO 3 Sulfonic acid electrolyte salts such as Li; liN (FCO) 2 ) 2 、LiN(FCO)(FSO 2 )、LiN(FSO 2 ) 2 、LiN(FSO 2 )(CF 3 SO 2 )、LiN(CF 3 SO 2 ) 2 、LiN(C 2 F 5 SO 2 ) 2 Cyclic 1, 2-perfluoroethanedisulfonimide lithium, cyclic 1, 3-perfluoropropanedisulfonylimide lithium, and LiN (CF) 3 SO 2 )(C 4 F 9 SO 2 ) Imide electrolyte salts; liC (FSO) 2 ) 3 、LiC(CF 3 SO 2 ) 3 、LiC(C 2 F 5 SO 2 ) 3 Isomethyl electrolyte salts; oxalic acid electrolyte salts such as lithium difluorooxalato borate, lithium bis (oxalato) borate, lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, and lithium tris (oxalato) phosphate; liPF (liquid crystal display) and LiPF 4 (CF 3 ) 2 、LiPF 4 (C 2 F 5 ) 2 、LiPF 4 (CF 3 SO 2 ) 2 、LiPF 4 (C 2 F 5 SO 2 ) 2 、LiBF 3 CF 3 、LiBF 3 C 2 F 5 、LiBF 3 C 3 F 7 、LiBF 2 (CF 3 ) 2 、LiBF 2 (C 2 F 5 ) 2 、LiBF 2 (CF 3 SO 2 ) 2 、LiBF 2 (C 2 F 5 SO 2 ) 2 And fluorine-containing organic electrolyte salts.
When the electrolyte salt is selected from other salts such as sodium salt, potassium salt, magnesium salt, zinc salt, or aluminum salt, lithium in the above lithium salt may be correspondingly changed to sodium, potassium, magnesium, zinc, or aluminum.
In a preferred embodiment, the sodium salt is selected from sodium perchlorate (NaClO) 4 ) Sodium hexafluorophosphate (NaPF) 6 ) Sodium tetrafluoroborate (NaBF) 4 ) At least one of sodium triflate (NaFSI) and sodium bis (NaTFSI).
In general, the electrolyte salt in the electrolyte is a transfer unit of lithium ions, and the concentration of the electrolyte salt directly affects the transfer rate of lithium ions, which affects the potential change of the negative electrode. In the process of quick battery charging, the moving speed of lithium ions needs to be improved as much as possible, the formation of lithium dendrites caused by too fast negative electrode potential drop is prevented, potential safety hazards are brought to the battery, and meanwhile, the too fast attenuation of the circulating capacity of the battery can be prevented. Preferably, the total concentration of the electrolyte salt in the electrolyte may be 0.5 to 2.0mol/L, 0.5 to 0.6mol/L, 0.6 to 0.7mol/L, 0.7 to 0.8mol/L, 0.8 to 0.9mol/L, 0.9 to 1.0mol/L, 1.0 to 1.1mol/L, 1.1 to 1.2mol/L, 1.2 to 1.3mol/L, 1.3 to 1.4mol/L, 1.4 to 1.5mol/L, 1.5 to 1.6mol/L, 1.6 to 1.7mol/L, 1.7 to 1.8mol/L, 1.8 to 1.9mol/L, or 1.9 to 1.3mol/L, and preferably, 1.7 to 1.8mol/L, and more preferably, 0.7 to 1.8 mol/L.
In some embodiments, the nonaqueous electrolyte further includes an auxiliary additive, wherein the auxiliary additive includes at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound;
in a preferred embodiment, the cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate, or vinyl methyl sulfate;
the sultone compound is at least one selected from methyl disulfonic acid methylene ester, 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;
the cyclic carbonate compound is at least one selected from ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,
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in the structural formula 2, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group;
the phosphate compound is at least one selected from tri (trimethylsilane) phosphate and a compound shown in a structural formula 3:
in the structural formula 3, R 31 、R 32 、R 32 Each independently selected from the group consisting of C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group.
In a preferred embodiment, the unsaturated phosphate compound may be at least one of tri (trimethylsilane) phosphate, tripropylethyl phosphate, dipropargyl methyl phosphate, dipropargylethyl phosphate, dipropargylpropyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2, 2-trifluoroethyl phosphate, dipropargyl-3, 3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2, 2-trifluoroethyl phosphate, diallyl-3, 3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate.
The borate compound is selected from tris (trimethylsilane) borate;
the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanedinitrile, adiponitrile, pimelic dinitrile, suberonitrile, nonyldinitrile and decyldinitrile.
In other embodiments, the auxiliary additive may further include other additives that improve battery performance: for example, additives that enhance the safety performance of the battery, specifically flame retardant additives such as fluorophosphate and cyclophosphazene, or overcharge-preventing additives such as t-amyl benzene and t-butyl benzene.
In some embodiments, the auxiliary additive is added in an amount of 0.01% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
In general, the addition amount of any one of the optional substances in the auxiliary additive to the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, and more preferably 0.1 to 2%, unless otherwise specified. Specifically, the addition amount of any optional substance in the auxiliary additive may be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8.5%, 9%, 9.5%, 10%.
In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the fluoroethylene carbonate is added in an amount of 0.05% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
In some embodiments, the solvent comprises one or more of an ether solvent, a nitrile solvent, a carbonate solvent, and a carboxylate solvent.
In some embodiments, the ether solvent includes cyclic or chain ethers, preferably chain ethers of 3 to 10 carbon atoms and cyclic ethers of 3 to 6 carbon atoms, which may be specifically but not limited to 1, 3-Dioxolane (DOL), 1, 4-Dioxane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH) 3 -THF), 2-trifluoromethyl tetrahydrofuran (2-CF) 3 -THF) one or more of; the chain ether may be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Since the chain ether has high solvation ability with lithium ions and can improve ion dissociation properties, dimethoxymethane, diethoxymethane and ethoxymethoxymethane, which have low viscosity and can impart high ion conductivity, are particularly preferable. The ether compound may be used alone, or two or more of them may be used in any combination and ratio. The amount of the ether compound to be added is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the highly compacted lithium ion battery of the present invention, and is usually 1% or more, preferably 2% or more, more preferably 3% or more in terms of the volume ratio of the nonaqueous solvent of 100%, and is usually 30% or less, preferably 25% or less, more preferably 20% or less in terms of the volume ratio. When two or more ether compounds are used in combination, the total amount of the ether compounds may be set to satisfy the above range. When the amount of the ether compound is within the above preferred range, the effect of improving the ionic conductivity due to the increase in the dissociation degree of lithium ions and the decrease in the viscosity of the chain ether can be easily ensured. In addition, when the negative electrode active material is a carbon material, co-intercalation of the chain ether and lithium ions can be suppressed, and thus the input/output characteristics and the charge/discharge rate characteristics can be brought into appropriate ranges.
In some embodiments, the nitrile solvent may be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile.
In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, which may be specifically but not limited to one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), gamma-butyrolactone (GBL), butylene Carbonate (BC); the chain carbonate may be, but is not limited to, in particular, one or more of dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the secondary battery of the present invention, but in the case where one is used alone, the lower limit of the content thereof is usually 3% by volume or more, preferably 5% by volume or more, relative to the total amount of the solvent of the nonaqueous electrolytic solution. By setting the range, it is possible to avoid a decrease in conductivity due to a decrease in dielectric constant of the nonaqueous electrolyte solution, and it is easy to achieve a good range of high-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting the range, the oxidation/reduction resistance of the nonaqueous electrolytic solution can be improved, thereby contributing to improvement of stability at high-temperature storage. The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more, based on the total amount of the solvent of the nonaqueous electrolytic solution. In addition, the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. By setting the content of the chain carbonate in the above range, the viscosity of the nonaqueous electrolytic solution can be easily set to an appropriate range, and the decrease in the ionic conductivity can be suppressed, thereby contributing to the improvement in the output characteristics of the nonaqueous electrolyte battery. When two or more kinds of chain carbonates are used in combination, the total amount of the chain carbonates may be set to satisfy the above range.
In some embodiments, it may also be preferable to use a chain carbonate having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonate"). The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. In the case where the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.
The carboxylic acid ester solvent includes a cyclic carboxylic acid ester and/or a chain carbonate. Examples of the cyclic carboxylic acid ester include: one or more of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone. Examples of the chain carbonate include, for example: one or more of Methyl Acetate (MA), ethyl Acetate (EA), propyl acetate (EP), butyl acetate, propyl Propionate (PP) and butyl propionate.
In some embodiments, the sulfone-based solvent includes cyclic sulfones and chain sulfones, preferably compounds having generally 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms in the case of cyclic sulfones, and generally 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms in the case of chain sulfones. The amount of the sulfone-based solvent to be added is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the secondary battery of the present invention, and is usually 0.3% or more, preferably 0.5% or more, more preferably 1% or more by volume, and is usually 40% or less, preferably 35% or less, more preferably 30% or less by volume, based on the total amount of the solvent of the nonaqueous electrolyte. When two or more sulfone solvents are used in combination, the total amount of sulfone solvents may be set to satisfy the above range. When the amount of the sulfone-based solvent added is within the above range, an electrolyte solution excellent in high-temperature storage stability tends to be obtained.
In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.
In some embodiments, a separator is further included in the secondary battery, the separator being positioned between the positive electrode and the negative electrode.
The separator may be an existing conventional separator, and may be a polymer separator, a non-woven fabric, etc., including but not limited to a single-layer PP (polypropylene), a single-layer PE (polyethylene), a double-layer PP/PE, a double-layer PP/PP, a triple-layer PP/PE/PP, etc.
The invention is further illustrated by the following examples.
The compounds referred to in the following examples and comparative examples are shown in the following table:
table 1 examples and comparative examples designs of parameters
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Example 1
This example is for illustrating the secondary battery and the method of manufacturing the same disclosed in the present invention, and includes the following steps:
1) Preparation of nonaqueous electrolyte
Mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) according to the mass ratio of EC:DEC:EMC=3:2:5, and then adding lithium hexafluorophosphate (LiPF) 6 ) The additives and the contents thereof were shown in Table 1, based on 100% by mass of the total nonaqueous electrolytic solution, to a molar concentration of 1 mol/L.
2) Preparation of positive electrode plate
Mixing an anode active material, a conductive agent Super-P and a binder polyvinylidene fluoride (PVDF) according to the mass ratio NCM523 to conductive carbon black Super-P of the conductive agent and the binder polyvinylidene fluoride=97:1.4:1.6, adding N-methylpyrrolidone (NMP), and uniformly mixing to prepare anode slurry of the lithium ion battery; the positive electrode active material is selected as shown in table 1, the positive electrode slurry is coated on a current collector aluminum foil, the current collector aluminum foil is dried at 85 ℃, then cold-pressed, the single-sided surface density is shown in table 1, then the current collector aluminum foil is subjected to trimming, cutting and slitting, then the current collector aluminum foil is dried for 24 hours under the vacuum condition at 85 ℃, and the tab is welded, so that the positive electrode plate of the lithium ion battery is prepared.
3) Preparation of negative electrode plate
Dispersing negative electrode active material graphite, conductive carbon black, thickener CMC and binder SBR in solvent deionized water according to the mass ratio of 96:1:1:2, and uniformly mixing to obtain negative electrode slurry; uniformly coating the negative electrode slurry on a negative electrode current collector copper foil; and drying, cold pressing, slitting and cutting to obtain the negative electrode plate.
4) Preparation of the cell
And placing a lithium battery diaphragm between the positive plate and the negative plate, winding a sandwich structure formed by the positive plate, the negative plate and the diaphragm, flattening the winding body, putting the flattened winding body into an aluminum plastic film, respectively leading out outgoing lines of the positive and negative electrodes, and thermally pressing and sealing the aluminum plastic film to obtain the battery cell to be injected with the liquid.
5) Injection and formation of battery cell
In a glove box with the dew point controlled below-40 ℃, the prepared electrolyte is injected into a dried cell, vacuum-packaged, kept stand for 24 hours, and then formed according to the following conditions: charging to 3.4V at constant current of 0.05C, charging to 3.85V at constant current of 0.1C, aging at 45 ℃ for 24h, exhausting, shaping, sealing, charging to 4.3V at constant current and constant voltage of 0.2C, stopping charging at 0.05C, standing for 5min, and discharging to 3.0V at multiplying power of 0.2C.
Examples 2 to 31
Examples 2 to 31 are for illustrating the battery and the method for manufacturing the same disclosed in the present invention, and include most of the operation steps in example 1, which are different in that:
the electrolyte additive components and the positive electrode material layer shown in table 1 were used.
Comparative examples 1 to 18
Comparative examples 1 to 18 are for illustrating the battery and the method for manufacturing the same disclosed in the present invention, and include most of the operation steps of example 1, which are different in that:
the electrolyte additive components and the positive electrode material layer shown in table 1 were used.
Performance testing
The lithium ion battery prepared by the method is subjected to the following performance test:
1) Thermal shock test of lithium ion battery: the lithium ion batteries prepared in examples and comparative examples were left to stand for 5 minutes at 25 ℃, charged to 4.3V at a constant current of 1C magnification, charged to a current of 0.05C or less at a constant voltage, and left to stand for 5 minutes. Then the lithium ion battery is placed in an oven, the temperature of the oven is set to be increased from 25 ℃ to 130 ℃ at the heating rate of 2 ℃/min, and the temperature is kept for 2 hours. The temperature of the battery surface is monitored during the temperature rising process and the heat preservation process.
2) High temperature cycle performance test of lithium ion battery: the formed battery was charged to 4.3V at 45C with a constant current and constant voltage of 1C, and then charged at constant voltage until the current was reduced to 0.05C, and then discharged to 3.0V with a constant current of 1C, and thus circulated, the discharge capacity at week 1 and the discharge capacity at week 500 were recorded.
The capacity retention for the high temperature cycle was calculated as follows:
capacity retention= (discharge capacity at 500 th week/discharge capacity at 1 st week) ×100%.
3) High-temperature storage performance test of lithium ion battery:
and (3) placing the lithium ion battery at 25 ℃ for 5 minutes, charging to 4.3V at a constant current with a multiplying power of 1C, charging to a current of less than or equal to 0.05C at a constant voltage, placing for 5 minutes, discharging to 3.0V at a constant current with a multiplying power of 1C, and testing to obtain the initial discharge capacity of the lithium ion battery.
At 25 ℃, the lithium ion battery is placed for 5 minutes, is charged to 4.3V at a constant current with a multiplying power of 1C, is charged at a constant voltage until the current is less than or equal to 0.05C, is placed for 5 minutes, and is placed in an oven at 60 ℃ for 30 days.
And taking out the lithium ion battery stored at high temperature for 30 days, naturally cooling to 25 ℃, discharging to 3.0V at constant current with 1C multiplying power, and testing to obtain the discharge capacity of the lithium ion battery stored at high temperature for 30 days.
The capacity retention (%) = (discharge capacity after 30 days of high temperature storage/initial discharge capacity) ×100% after 30 days of high temperature storage of the lithium ion battery.
(1) The test results obtained in examples 1 to 22 and comparative examples 1 to 18 are filled in Table 2.
TABLE 2
From the test results of examples 1 to 22 and comparative examples 1 to 18, it can be seen that when the ratio W of the mass of the nonaqueous electrolytic solution to the rated capacity of the secondary battery, the mass percentage u of the compound represented by structural formula 1 in the nonaqueous electrolytic solution, the mass percentage q of the manganese element in the positive electrode material layer, and the single-sided area density s of the positive electrode material layer satisfy the relationship: w/(q×s) is less than or equal to 0.05 and less than or equal to 100×W×u/(q×s) is less than or equal to 5, W is less than or equal to 2.0g/Ah and less than or equal to 4.5g/Ah, u is less than or equal to 0.05% and less than or equal to 3.5%, q is less than or equal to 5% and less than or equal to 65%, and 10mg/cm 2 ≤s≤30mg/cm 2 In the process, the compound shown in the structural formula 1 is subjected to oxidative decomposition on the surface of the positive electrode material layer, and a passivation film combined with manganese element is formed on the surface of the manganese-based material, so that the positive electrode active material can be effectively prevented from being in direct contact with the nonaqueous electrolyte, the buffer and ion exchange effects are provided, meanwhile, the compound is reacted with manganese in the manganese-based material to inhibit disproportionation reaction, further, the dissolution of manganese ions of the manganese-based material can be effectively inhibited, the high-temperature stability of the battery electrode material and the nonaqueous electrolyte is improved, and the thermal shock resistance, the high-temperature storage performance and the high-temperature cycle performance of the battery are improved.
As can be seen from the test results of comparative examples 2, 3, 10, 11, 13 to 17, even if the W value, the u value, the q value, and the s value all satisfy the parameter range definition thereof, the relational expression is not satisfied: when the mass percentage of the compound shown in the structural formula 1 in the nonaqueous electrolyte is equal to or less than 100 XW multiplied by u/(q multiplied by s) and is equal to or less than 5, the high-temperature storage and cycle performance of the battery still cannot reach a better level, and the effect of mutual influence exists among the mass percentage u of the compound shown in the structural formula 1 in the nonaqueous electrolyte, the mass percentage q of the manganese element in the positive electrode material layer and the single-sided surface density s of the positive electrode material layer, and the electrochemical performance of the battery at high temperature can be improved if and only if the four are in an equilibrium state. Meanwhile, as is clear from the test results of comparative examples 1, 4 to 9, 12, 18, when one parameter in W, u, q, s exceeds the limit range, even if the relation is satisfied: the requirement that the ratio W of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery, the mass percentage U of the compound shown in the structural formula 1 in the nonaqueous electrolyte, the mass percentage q of the manganese element in the positive electrode material layer and the single-sided surface density s of the positive electrode material layer are in strong relevance, when the ratio W of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery and the single-sided surface density s of the positive electrode material layer directly influence the infiltration effect of the compound shown in the structural formula 1 in the positive electrode material layer, the decomposition ratio and the compactness degree of the compound shown in the structural formula 1 in the formed passivation film and the bonding strength with the manganese-based material are further influenced, and when the formed passivation film is not compact enough or the bonding force with the manganese-based material is not enough, a good protective effect cannot be formed on the manganese-based material layer, so that the dissolution of Mn ions is caused, and the promotion of the high temperature performance and the thermal shock resistance of the battery is not facilitated.
As is apparent from the test results of examples 7 to 10, with the increase of the mass percentage content u of the compound represented by structural formula 1 in the nonaqueous electrolyte, the high temperature performance of the battery is gradually increased, and it is revealed that the passivation film formed on the surface of the positive electrode material layer by the compound represented by structural formula 1 can effectively avoid direct contact of the positive electrode active material with the nonaqueous electrolyte, and the elution of manganese ions is suppressed, but when the compound represented by structural formula 1 is added in excess, the high temperature performance of the battery is rather lowered, presumably because the impedance of the passivation film is increased due to the addition of the compound represented by structural formula 1 in excess, and thus the capacity of the battery is not exhibited at high temperature.
As shown by the test results of examples 11 to 22, when different manganese-based materials were used as the positive electrode active materials, the manganese element in the manganese-based material had a good synergistic effect with the compound represented by structural formula 1, which indicated that the manganese element in the manganese-based material was a key element to be combined with the compound represented by structural formula 1, and the thermal shock resistance of the battery was gradually enhanced as the manganese content of the positive electrode material layer was gradually increased, but the high temperature cycle and high temperature storage performance of the battery were lowered, because the manganese element in the positive electrode active material was unstable at high temperature and was liable to cause dissolution problems, but the mass percentage content u of the compound represented by structural formula 1 in the nonaqueous electrolyte and the single-sided surface density s of the positive electrode material layer were limited, and the thickness and mass of the manganese-based material surface passivation film could be controlled, thereby effectively reducing the battery impedance and suppressing dissolution of manganese ions, and improving the high temperature electrochemical performance of the battery.
(2) The test results obtained in examples 14, 23 to 27 are filled in Table 3
TABLE 3 Table 3
As is clear from the test results in Table 3, in examples 14 and 23 to 27, when the different compounds of the formula 1 were used, the same conditions were satisfied that 0.05.ltoreq.100 XW.times.u/(q.times.s). Ltoreq.5 and the ranges for the W value, u value, q value and S value were defined, which revealed that the cyclic sulfate groups contained in the different compounds of the formula 1 had decisive effects in participating in the formation of the passivation film on the manganese-based material surface, and that the passivation film rich in S element produced by decomposition had a good bonding strength with the manganese-based material, inhibiting elution of manganese ions in the manganese-based material, and at the same time avoiding the catalytic decomposition effect of the manganese-based material on the nonaqueous electrolyte, thereby having a general improvement in the high temperature performance of the battery.
(3) The test results obtained in examples 14, 28 to 31 are filled in Table 4
TABLE 4 Table 4
As shown in the test results of Table 4, on the basis of the lithium ion battery system provided by the invention, PS, DTD, tripropylester phosphate, succinonitrile and the like are added as auxiliary additives, so that the cycle performance of the battery can be further improved, the chain length of a product component obtained by decomposing a small-molecule cyclic S-containing compound contained in PS and DTD is presumed to be shorter than that of a decomposition product of a compound shown in a structural formula 1, the gap of a passivation film formed by the compound shown in the structural formula 1 can be filled, the tripropylester phosphate and the succinonitrile also have lower reduction potential, and phosphorus and nitrogen contained in the tripropylester phosphate and the succinonitrile play a role in reinforcing the passivation film so as to form a more stable passivation film structure on the surface of an electrode, so that the high-temperature storage stability and the high-temperature cycle capacity retention rate of the battery are improved.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (7)

1. A secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material comprising a manganese-based material selected from the group consisting of compounds represented by the formula (A)
Li 1+x Ni a Co b M’ 1-a-b O 2-y A y (A)
In the formula (A), x is more than or equal to 0.1 and less than or equal to 0.2,0 is less than or equal to a <1,0 is less than or equal to b is less than or equal to 1,0 is less than or equal to a+b is less than 1,0 is less than or equal to y is less than or equal to 0.2, M' comprises Mn, and comprises Al, sr, mg, ti, ca, zr, zn, si, fe, zero species, one or more species of Ce, A comprises S, N, F, B, cl, br and one or more species of I;
the nonaqueous electrolytic solution includes a solvent, an electrolyte salt, and an additive including a compound represented by structural formula 1:
wherein n is 0 or 1, A is selected from C or O, and X is selected fromR 1 、R 2 Each independently selected from H, R 1 And R is 2 Not simultaneously selected from H, and X, R 1 And R is 2 Contains at least one sulfur atom;
the secondary battery satisfies the following conditions:
0.1≤100×W×u/(q×s)≤4；
w is more than or equal to 2.0g/Ah and less than or equal to 3.5g/Ah, u is more than or equal to 0.05% and less than or equal to 3.5%, q is more than or equal to 11.33% and less than or equal to 50%, and 10mg/cm 2 ≤s≤30mg/cm 2 ；
Wherein W is the ratio of the mass of the nonaqueous electrolyte to the rated capacity of the secondary battery, and the unit is g/Ah;
u is the mass percentage content of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is;
q is the mass percentage content of manganese element in the positive electrode material layer, and the unit is;
s is the single-sided area density of the positive electrode material layer, and the unit is mg/cm 2 。
2. The secondary battery according to claim 1, wherein the compound represented by structural formula 1 has a mass percentage u in the nonaqueous electrolytic solution of 0.05% to 3.0%.
3. The secondary battery according to claim 1, wherein the single-sided area density s of the positive electrode material layer is 15 to 25mg/cm 2 。
4. The secondary battery according to claim 1, wherein the compound represented by structural formula 1 is selected from one or more of the following compounds 1 to 22:
5. the secondary battery according to claim 1, wherein the nonaqueous electrolytic solution further comprises an auxiliary additive, and the auxiliary additive comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound.
6. The secondary battery according to claim 5, wherein the additive is added in an amount of 0.01% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
7. The secondary battery according to claim 5, wherein the cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate, or vinyl methyl sulfate;
the sultone compound is at least one selected from methyl disulfonic acid methylene ester, 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;
the cyclic carbonate compound is at least one selected from ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,
in the structural formula 2, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group;
the phosphate compound is at least one selected from tri (trimethylsilane) phosphate and a compound shown in a structural formula 3:
in the structural formula 3, R 31 、R 32 、R 33 Each independently selected from the group consisting of C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
The borate compound is selected from tris (trimethylsilane) borate;
the nitrile compound is selected from one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanedinitrile, adiponitrile, pimelic dinitrile, suberonitrile, nonyldinitrile and decyldinitrile.
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